cc: Fix for synced property main thread updates with MFBA.

cc/trees/layer_tree_host_unittest_scroll.cc

Index: cc/trees/layer_tree_host_unittest_scroll.cc
diff --git a/cc/trees/layer_tree_host_unittest_scroll.cc b/cc/trees/layer_tree_host_unittest_scroll.cc
index 5d22eb80aa18cedcc9f3b15617221f99ad168c02..6c0623b699ae072da6060f7a8253fff579740cf7 100644
--- a/cc/trees/layer_tree_host_unittest_scroll.cc
+++ b/cc/trees/layer_tree_host_unittest_scroll.cc
@@ -8,6 +8,7 @@
 #include "base/memory/weak_ptr.h"
 #include "base/single_thread_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
+#include "cc/base/completion_event.h"
 #include "cc/input/main_thread_scrolling_reason.h"
 #include "cc/layers/layer.h"
 #include "cc/layers/layer_impl.h"
@@ -1513,5 +1514,127 @@ TEST_F(LayerTreeHostScrollTestLayerStructureChange, ScrollDestroyWholeTree) {
   RunTest(CompositorMode::THREADED, false);
 }
 
+class LayerTreeHostScrollTestScrollMFBA : public LayerTreeHostScrollTest {
+ public:
+  LayerTreeHostScrollTestScrollMFBA()
+      : initial_scroll_(10, 20),
+        second_scroll_(40, 5),
+        scroll_amount_(2, -1),
+        num_commits_(0),
+        num_scrolls_(0) {}
+
+  void InitializeSettings(LayerTreeSettings* settings) override {
+    settings->main_frame_before_activation_enabled = true;
+  }
+
+  void BeginTest() override {
+    outer_viewport_container_layer_id_ = layer_tree_host()
+                                             ->outer_viewport_scroll_layer()
+                                             ->scroll_clip_layer()
+                                             ->id();
+    layer_tree_host()->outer_viewport_scroll_layer()->SetScrollOffset(
+        initial_scroll_);
+    PostSetNeedsCommitToMainThread();
+  }
+
+  void StartCommitOnImpl() override {
+    switch (num_commits_) {
+      case 0:
+        PostSetNeedsCommitToMainThread();
+        break;
+      case 1:
+        PostSetNeedsCommitToMainThread();
+        // Block activation after second commit until third commit is ready.
+        GetProxyImplForTest()->BlockNotifyReadyToActivateForTesting(true);
+        break;
+      case 2:
+        // Unblock activation after third commit is ready.
+        GetProxyImplForTest()->BlockNotifyReadyToActivateForTesting(false);
+        break;
+    }
+    num_commits_++;
+  }
+
+  void UpdateLayerTreeHost() override {
+    Layer* scroll_layer = layer_tree_host()->outer_viewport_scroll_layer();
+    switch (layer_tree_host()->source_frame_number()) {
+      case 0:
+        EXPECT_VECTOR_EQ(initial_scroll_, scroll_layer->scroll_offset());
+        break;
+      case 1:
+        EXPECT_VECTOR_EQ(
+            gfx::ScrollOffsetWithDelta(initial_scroll_, scroll_amount_),
+            scroll_layer->scroll_offset());
+
+        // Pretend like Javascript updated the scroll position itself.
+        scroll_layer->SetScrollOffset(second_scroll_);
+        break;
+      case 2:
+        // Third frame does not see a scroll delta because we only did one
+        // scroll for the second and third frames.
+        EXPECT_VECTOR_EQ(second_scroll_, scroll_layer->scroll_offset());
+        break;
+    }
+  }
+
+  void DrawLayersOnThread(LayerTreeHostImpl* impl) override {
+    LayerImpl* root = impl->active_tree()->root_layer();
+    LayerImpl* scroll_layer = impl->OuterViewportScrollLayer();
+    EXPECT_VECTOR_EQ(gfx::Vector2d(), ScrollDelta(scroll_layer));
+
+    scroll_layer->SetScrollClipLayer(outer_viewport_container_layer_id_);
+    scroll_layer->SetBounds(
+        gfx::Size(root->bounds().width() + 100, root->bounds().height() + 100));
+    scroll_layer->ScrollBy(scroll_amount_);
+
+    switch (num_commits_) {
+      case 1:
+        EXPECT_VECTOR_EQ(initial_scroll_, ScrollTreeForLayer(scroll_layer)
+                                              ->GetScrollOffsetBaseForTesting(
+                                                  scroll_layer->id()));
+        EXPECT_VECTOR_EQ(scroll_amount_, ScrollDelta(scroll_layer));
+
+        break;
+      case 2:
+        EXPECT_VECTOR_EQ(second_scroll_, ScrollTreeForLayer(scroll_layer)
+                                             ->GetScrollOffsetBaseForTesting(
+                                                 scroll_layer->id()));
+        EXPECT_VECTOR_EQ(scroll_amount_, ScrollDelta(scroll_layer));
+        break;
+      case 3:
+        EXPECT_VECTOR_EQ(second_scroll_, ScrollTreeForLayer(scroll_layer)
+                                             ->GetScrollOffsetBaseForTesting(
+                                                 scroll_layer->id()));
+        // Two scrolls haven't been consumed by the main thread.
+        EXPECT_VECTOR_EQ(scroll_amount_, ScrollDelta(scroll_layer));
+        EndTest();
+        break;
+    }
+  }
+
+  void ApplyViewportDeltas(const gfx::Vector2dF& inner_delta,
+                           const gfx::Vector2dF& outer_delta,
+                           const gfx::Vector2dF& elastic_overscroll_delta,
+                           float scale,
+                           float top_controls_delta) override {
+    num_scrolls_++;
+  }
+
+  void AfterTest() override {
+    EXPECT_EQ(3, num_commits_);
+    EXPECT_EQ(1, num_scrolls_);
+  }
+
+ private:
+  gfx::ScrollOffset initial_scroll_;
+  gfx::ScrollOffset second_scroll_;
+  gfx::Vector2dF scroll_amount_;
+  int num_commits_;
+  int num_scrolls_;
+  int outer_viewport_container_layer_id_;
+};
+
+MULTI_THREAD_TEST_F(LayerTreeHostScrollTestScrollMFBA);
+
 }  // namespace
 }  // namespace cc